Hydraulic diaphragm control

ABSTRACT

A diaphragm pump includes a pumping chamber for pumped fluid and a hydraulic chamber. A diaphragm has a pumping chamber side and a hydraulic chamber side. The pumping chamber side of the diaphragm is proximate the pumping chamber and acts on the pumped fluid. The hydraulic chamber side of the diaphragm is proximate the hydraulic chamber. A plunger is in fluid communication with the hydraulic chamber and acts on the hydraulic fluid, which acts on the diaphragm. A plunger driver imparts reciprocal motion to the plunger. The pump includes a sensor assembly sensing position and direction of the plunger and sensing position of the diaphragm. By sensing the position of the diaphragm, hydraulic fluid flow is controlled by a control single valve.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention is directed to a system for controlling adiaphragm in a diaphragm pump using a solenoid valve and to a pumpincluding a system using a solenoid valve to control the diaphragm.

Description of the Prior Art

Diaphragm pumps are pumps in which the pump fluid is displaced by adiaphragm. In hydraulically driven pumps, the diaphragm is deflected byhydraulic fluid pressure forced against the diaphragm, which actsagainst the pumped fluid in a reciprocating motion. Typically, a plungermoves in a reciprocating manner in a cylinder to act against thehydraulic fluid and force the fluid against the diaphragm. The hydraulicfluid flow is controlled by a system of valves. Such control systems fordiaphragm pumps are shown in U.S. Pat. No. 4,665,974 and U.S. Pat. No.7,425,120. Such a control system has three main valves for each cylinderincluding a spool valve, a check valve that relieves fluid in an overfilled condition, and a check valve utilized for adding fluid in anunder filled condition. For each of the check valves, a spool valvedepending on the diaphragm position is utilized for actuation. Inaddition, such diaphragm pumps also typically require a fourth valveused as an air bleed valve that allows air to exit the hydraulic chambersuch as may occur during priming.

Although such pumps and such control systems are generally efficient andreliable, the valves are relatively costly and require aninterrelationship to maintain the proper fluid level and pressure.Moreover, the pump must be configured with a hydraulic chamber thatallows for correct placement and interrelationship of the various valvesand their associated fluid conduits.

It can be seen that a new and improved pump and control system areneeded that eliminate one or more of the hydraulic fluid valves in adiaphragm pump and provide reliable pumping and control at a reducedcost. In particular, the reduction in the number of valves and sensorsto a single solenoid valve is desirable. The present invention addressesthese problems as well as others associated with diaphragm pumps anddiaphragm position control.

SUMMARY OF THE INVENTION

The present invention is directed to a diaphragm pump, and in particularto a diaphragm pump with a control system that utilizes a single valveto control fluid levels in the hydraulic chamber. The diaphragm isdriven by a plunger connected to a crankshaft or other drive. Thediaphragm includes a non-magnetic rod connecting to an iron rod that issensed by one or more proximity sensors.

The present invention includes a single solenoid valve connected to thehydraulic chamber that controls hydraulic fluid flow into or out of thehydraulic chamber to correct an overfill condition or underfillcondition. In different embodiments, the plunger may be driven by acrankshaft that may include a proximity sensor sensing indicator lobesof the crankshaft. In other embodiments, the plunger may be driven by alead screw and stepper motor.

The iron rod connected to the diaphragm may include a single sensorworking in conjunction with sensors on the lobes of the crankshaft ormay include two proximity sensors to detect the position of the iron rodand therefore the position of the diaphragm. In another embodiment, alinear variable differential transformer accurately detects the positionof the iron rod and therefore the position of the diaphragm. In eachembodiment, the sensors and sensing circuit and/or controller are ableto determine whether the plunger has gone beyond top dead center orbottom dead center and whether there is an underfilled condition or anoverfilled condition. When this occurs, the single solenoid valve may beopened or closed to correct the underfilled or overfilled condition. Theuse of multiple sensors eliminates the need for more than one hydraulicfluid control valve.

These features of novelty and various other advantages that characterizethe invention are pointed out with particularity in the claims annexedhereto and forming a part hereof. However, for a better understanding ofthe invention, its advantages, and the objects obtained by its use,reference should be made to the drawings that form a further parthereof, and to the accompanying descriptive matter, in which there isillustrated and described a preferred embodiment of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

Referring now to the drawings, wherein like reference letters andnumerals represent corresponding structure throughout the several views:

FIG. 1 is a schematic view of a diaphragm pump with a first embodimentof a sensing system;

FIG. 2 is a logic and wiring diagram for the diaphragm pump shown inFIG. 1;

FIG. 3 is a crankshaft for a 3 cylinder pump such as the pump shown inFIG. 1 with a sensor and indicator lobes for each cylinder;

FIG. 4 is a schematic view of diaphragm pump with a second embodiment ofa sensing system;

FIG. 5 is a schematic view of a diaphragm pump with a third embodimentof a sensing system;

FIG. 6 is a schematic view of a diaphragm pump with a fourth embodimentof a sensing system;

FIG. 7 is a schematic view of the diaphragm pump of FIG. 1 with thediaphragm in the bottom dead center (BDC) position;

FIG. 8 is a schematic view of the diaphragm pump of FIG. 1 with thediaphragm in the top dead center (TDC) position;

FIG. 9 is a schematic view of the diaphragm pump of FIG. 1 with thesolenoid open to add fluid to the under-filled hydraulic fluid chamberat BDC; and

FIG. 10 is a schematic view of the diaphragm pump of FIG. 1 with thesolenoid open to dump fluid from the over-filled hydraulic fluid chamberat TDC.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now to the drawings, and in particular FIG. 1, there is showna pump, generally designated (100). In particular, the pump (100) may bea diaphragm pump including a deformable diaphragm (102). The diaphragm(102) is deformed to act on pumped fluid in a fluid chamber (104). Flowinto and out of the pumped fluid chamber (104) is controlled by an inletcheck valve (106) and an outlet check valve (108). A hydraulic chamber(110) filled with hydraulic fluid is on the opposite side of thediaphragm (102). A plunger (116) reciprocates in a cylinder (114) to acton the hydraulic fluid, which acts on the diaphragm (102) to forcepumped fluid out as shown in FIG. 10 or to draw pump fluid in as shownin FIG. 9. The cylinder (116) is driven by a crankshaft (132) through aconnecting linkage (124).

The pump (100) also includes a tube (112) connected to the hydraulicchamber (110). The tube (112) is made of a non-metallic material so asnot to be affected by magnetics does not affect sensors able to sensemagnetic materials. The opposite end of the tube (112) is closed tocomplete a hydraulic space. The diaphragm (102) is connected to anon-metallic rod (122). An iron rod (120) mounts to the non-metallic rod(122) and reciprocates as the diaphragm (102) is moved outward into thepumping chamber (104) and retracted back against the hydraulic fluid inthe hydraulic fluid chamber (110).

In a first embodiment, a proximity sensor (150) is located proximate thetube (112) so that the sensor (150) can sense the iron rod (120) insidethe tube (112). The rod (122) and the tube (112) are both made frommaterials that the sensor (150) will not detect. It will be appreciatedthat the sensor (150) may be an inductive type sensor able to detect theiron rod (120) but not the connecting rod (122). The sensor (150) ispositioned so as to detect the rod (120) when the diaphragm (102) is atany position along its normal operating stroke. When the diaphragm (102)travels beyond top dead center when the hydraulic chamber (110) is inthe over-filled condition, or beyond bottom dead center when thehydraulic chamber (110) is in the under-filled condition, the sensor(150) does not detect the iron rod (120). This information is passedalong to a controller (142).

The pump (100) uses a single solenoid valve (140) connected to thehydraulic chamber (110) to control hydraulic fluid flow. In a preferredembodiment, the solenoid valve (140) is near the top of the hydraulicchamber (110) so that air can exit the hydraulic chamber (110) throughthe valve (140). The other port from the valve (140) is connected to afluid sump by tubing (118). The end of the tubing (118) should bepositioned below the surface of the fluid so that fluid can either exitor enter the tubing (118).

In the embodiment shown in FIG. 1, the pump control system also includesa second set of proximity sensors (154) proximate the crankshaft (132).The crankshaft (132) includes lobes (134). The lobes (134) arepositioned so that when sensed by sensor (154), the diaphragm is ateither top dead center or bottom dead center. The lobes (134) arepositioned so that as soon as the crank passes top dead center or bottomdead center, the sensor (154) stops detecting the lobes (134). Anembodiment of the crankshaft (132) is shown in greater detail in FIG. 3.The crankshaft (132) includes lobes (134) for each cylinder in a threecylinder pump.

Referring now to FIG. 2, there is shown a circuit diagram for thecontrol circuit (144). The control circuit (144) is connected to thesolenoid valve (140) as well as the proximity sensors (150 and 154).Switches (170 and 172) are energized or de-energized by the respectivesensor (150 or 154) to open or close the circuit (144) and thereforeopen or close the valve (140). Simple and reliable control is thereforeobtained with the circuit (144) requiring only two switches (170 and172).

The control circuit (144) connects to the proximity sensors (150 and154) and to the solenoid valve (140) and may also connect to amicrocontroller (142). Opening and closing of the solenoid valve (140)is controlled by the positions detected by the proximity sensors (150and 154). It can be appreciated that the relay energized by the sensor(150) is normally closed so that when the sensor (150) detects the rod(120) in normal operation, the circuit (144) is open.

Referring now to FIG. 4, there is shown a second embodiment of the pump(100). The pump shown in FIG. 4 is similar to that shown in FIG. 1 butthe pump utilizes a linear variable differential transformer (LVDT) todetect the iron rod (120). In the embodiment shown, the LVDT includesthree coils (162) that surround the fiberglass tube (112). Use of theLVDT avoids having electrical coils immersed in the fluid of thehydraulic chamber (110). This configuration also avoids feeding wiresinto the cycling high pressure of the chamber (110), which may bedifficult and complicated. The LVDT also provides a signal indicatingthe position of the diaphragm (102) throughout the stroke and achievesprecise timing for opening of the valve (140).

Referring now to FIG. 5, there is shown a third embodiment of adiaphragm pump. In the embodiment of FIG. 5, the plunger (116) is drivenby a linear drive (182) such as a lead screw and a stepper motor (180)that may be controlled by a controller (142). As the microcontroller(142) knows the position and direction of the plunger from inputs fromthe stepper motor (180), the microcontroller can thereforeinfer/determine the proximate position of the diaphragm. Therefore, onlyone proximity sensor is required to indicate an under-fill or anover-fill condition. The proximity sensor (150) is placed mid stroke ofthe iron rod (120). Therefore, when the stroke of the diaphragm (102)exceeds the normal range in either direction, the sensor (150) signalsthe microcontroller (142). In response to the sensed under-fill orover-fill condition, the microcontroller (142) will open the solenoidvalve (140) at an appropriate time to restore normal operatingconditions.

Referring now to FIG. 6, there is shown a fourth embodiment of a pump.In the embodiment shown in FIG. 6, the pump (100) utilizes two proximitysensors (150 and 152) to detect the position of the diaphragm. Thesensor (152) acts as an under-fill sensor and detects the position of aniron rod (120). By using two sensors (150 and 152) to detect theposition of the rod (120), the controller (142) will be able todetermine whether the diaphragm is beyond the top dead centerover-filled condition or beyond the bottom dead center under-filledposition regardless of the position of the plunger (116). With the twospaced apart proximity sensors (150 and 152), only the direction of theplunger (160) is needed rather than the position of the crank (132)relative to top dead center or bottom dead center.

It can be appreciated that the operation of the solenoid valve operatesin four main modes. The logic used to open the solenoid valve (140) issimilar in each of the four embodiments. However, the general operationis described with respect to the embodiment of FIG. 1 even thoughapplicable to the other embodiments. In a first mode, the pump is in anormal operating mode. In a second mode, the pump is in an under-filledoperating mode. In a third mode, the pump is in an over-filled operatingmode, and in a fourth mode, the pump is in a priming condition. Thefirst mode is shown in FIGS. 7 and 8. In the first operating mode, thepump (100) has the correct amount of fluid in the hydraulic chamber(110). The pump (100) is shown with the diaphragm (102) and the plunger(116) at bottom dead center in FIG. 7. At this position, the sensor(150) still detects the rod (120) so the solenoid valve (140) remainsclosed. With the pump (100) shown with the diaphragm (102) and theplunger (116) at top dead center in FIG. 8, the sensor (150) detects theiron rod (120) and the solenoid valve (140) remains closed.

As shown in FIG. 9, in the second mode, the plunger (116) is approachingbottom dead center but the diaphragm (102) has passed beyond the normalbottom dead center and the proximity sensor (150) is not sensing the rod(120). The control circuit (144) opens the solenoid valve (140). As theplunger (116) continues to bottom dead center, hydraulic fluid is drawninto the hydraulic chamber (110). The solenoid valve (140) closes oncethe sensor (154) senses that the plunger (116) has reached bottom deadcenter and is beginning the forward pressure stroke.

As shown in FIG. 10, in the third operating mode, the plunger (116) isapproaching top dead center but the diaphragm (102) has gone beyond thenormal top dead center position and the proximity sensor (150) is notsensing the rod (120). A microcontroller or the control circuit (144)opens the solenoid valve (140). As the plunger (116) continues to topdead center, hydraulic fluid is dumped from the hydraulic chamber (110).Once the plunger (116) is at top dead center, the second set ofproximity sensors (154) senses top dead center from the lobes (134) andshuts the valve (140) for the suction stroke.

The fourth mode takes place when the pump (100) is first assembled andhydraulic oil needs to be primed into the hydraulic chamber (110). Inthis scenario, the solenoid valve (140) is held open for several strokesby the microcontroller regardless of input from the sensors (150 and154) to purge air from the hydraulic chamber (110). After severalstrokes, the valve (140) is closed and depending on which mode the pumpis in after the solenoid valve (140) is closed, the oil level in thehydraulic chamber (110) will be automatically adjusted by the controllerto return to normal.

It can be appreciated that the present invention achieves improvedcontrol utilizing sensors to detect the true position of the diaphragm.Control of the fluid levels is accomplished with a single solenoid valve(140) and eliminates the need for multiple valves associated with thehydraulic chamber as is required with the prior art. The presentinvention achieves greater reliability and is less expensive and easierto manufacture and maintain.

It is to be understood, however, that even though numerouscharacteristics and advantages of the present invention have been setforth in the foregoing description, together with details of thestructure and function of the invention, the disclosure is illustrativeonly, and changes may be made in detail, especially in matters of shape,size and arrangement of parts within the principles of the invention tothe full extent indicated by the broad general meaning of the terms inwhich the appended claims are expressed.

What is claimed is:
 1. A diaphragm pump comprising: a pumping chamber; ahydraulic chamber; a diaphragm having a pumping chamber side and ahydraulic chamber side, the pumping chamber side being proximate thepumping chamber and the hydraulic chamber side being proximate thehydraulic chamber; a plunger in fluid communication with the hydraulicchamber; a plunger driver imparting reciprocal motion to the plunger; asensor assembly sensing position and direction of the plunger andsensing position of the diaphragm.
 2. The diaphragm pump according toclaim 1, further comprising a valve in fluid communication with thehydraulic chamber.
 3. The diaphragm pump according to claim 2, whereinthe plunger driver comprises a stepper motor.
 4. The diaphragm pumpaccording to claim 3, further comprising a controller in communicationwith the sensor assembly, the stepper motor and the valve, wherein thesensor assembly.
 5. The diaphragm pump according to claim 1, wherein theplunger drive comprises a crankshaft and wherein the sensor assemblycomprises a first crankshaft sensor sensing position of the crankshaft.6. The diaphragm pump according to claim 1, wherein the diaphragmcomprises a diaphragm rod extending from the hydraulic chamber side andwherein the sensor assembly comprises a sensor sensing a position of thediaphragm rod
 7. The diaphragm pump according to claim 1, wherein thediaphragm comprises a diaphragm rod extending from the hydraulic chamberside and wherein the sensor assembly comprises a first sensor and asecond sensor spaced apart from the first sensor, the first sensor andthe second sensor sensing a position of the diaphragm rod.
 8. Thediaphragm pump according to claim 1, wherein the diaphragm comprises adiaphragm rod extending from the hydraulic chamber side and wherein thesensor assembly comprises a linear variable differential transformer(LVDT) sensing a position of the diaphragm rod.
 9. The diaphragm pumpaccording to claim 1, wherein the plunger drive comprises a crankshaftand wherein the sensor assembly comprises a first crankshaft sensorsensing position of the crankshaft and a second crankshaft sensorsensing the position of the crankshaft.
 10. A diaphragm pump sensing andcontrol system, the diaphragm pump comprising a diaphragm, a hydraulicfluid chamber and a plunger acting on the hydraulic fluid chamber; thediaphragm pump sensing system comprising: a first sensor sensingposition and direction of the plunger; and a second sensor sensingposition of the diaphragm; a single valve controlling fluid flow intoand out of the hydraulic fluid chamber.
 11. A method for controlling adiaphragm pump, the diaphragm pump comprising a diaphragm, a fluidchamber containing hydraulic fluid acting on the diaphragm, a plunger influid communication with the fluid chamber, and a single valvecontrolling flow into and out of the fluid chamber, the methodcomprising: sensing position and direction of the plunger; sensingposition and direction of movement of the diaphragm;